The secretory immune system encompasses a group of localized antibody responses whose characteristics, functions and product antibody are difficult to evaluate. Secretory antibodies appear to play specific roles in enhanced resistance to a variety of infectious agents. The proposed investigations are designed to study the molecular diversity of secretory antibodies in order to assess the immune potential of the secretory antibody response. Information from these studies will be used to describe the functional capacities of the localized immune response and its relationship to the total immune process. The structural features of secretory IgA allow it to be differentiated from its serum counterpart and provide the marker immunoglobulin class neccessary for monitioring the secretory antibody response. The studies make use of a rabbit model system which is used for reproducible induction of secretory IgA antibodies. The binding properties and heterogeneity of these antibodies will be assessed. In addition to the high resolution technique of isoelectric focusing, additional probes will be used to study the products of antibody producing cells. Methodology previously employed to study DNP-antibody producing cell clones will be used for this purpose. These probes will be used to assess the "memory" and learning capabilities of the secretory antibody response. BIBLIOGRAPHIC REFERENCES: Montgomery, P.C., Rockey, J.H., Kahn, R.L. and Skandera, C.A. 1975. Molecular restriction of anti-DNP antibodies induced by (DNP)2-gramicidin S. J. Immunol., 115: 904-910. Montgomery, P.C., Skandera, C.A. and Kahn, R.L. 1975. Evidence for the induction of two antibodies with identical combining sites in outbred animals. Nature. 256: 138-140.